It is known in the field of automated stage lighting to include lighting instruments having motorized controls for adjusting the azimuth and elevation, the color, and the angle of divergence of the light beam.
One mechanism which is commonly used for adjusting the color of the light beam includes a scrolling gel changer, which is a motorized remotely-controlled device for exchanging colored sheets of transparent plastic material disposed in front of conventional lighting instruments. For example, the scrolling gel changer may be installed in a Par 64 incandescent lamp for color adjustment.
For improved color changing effects, dichroic filters are used in place of the color gels. The VARI*LITE.RTM. VL3.TM. automated wash luminaire includes a 475 watt incandescent lamp and a motorized cross-fading color changer which utilizes multiple sets of pivoting dichroic color filters. This, lighting instrument, disclosed in U.S. Pat. Nos. 4,392,187 and 4,602,321, both granted to J. Bornhorst, combines the pioneering dichroic filter color changing technology with incandescent light. The VARI*LITE.RTM. VL4.TM. automated wash luminaire combines the motorized cross-fading dichroic filter color changer with a 400 watt arc lamp, which combination produces, in addition to a wide range of other hues, many dramatic blue hues owing to the spectral characteristics of arc lamps.
According to the present invention, a new configuration of pivoting dichroic color filters in a radial arrangement is introduced. This configuration is especially well-suited for placement in the front of a large circular lamp such as a Par 64.
Another aspect of the invention of the present application relates to a drive arrangement which removes the disadvantages associated with gear driven mechanisms. For example, in a gear driven color filter assembly, the ring gear and filter gears must be fabricated to close tolerances and mounted in precisely maintained relation to each other to avoid problems associated with the meshing of the gear teeth. Gear mesh must be properly adjusted to eliminate backlash or else the accuracy and precision of the color changer will suffer. Gear mesh must also be properly maintained to avoid excessive friction between gears which results in excessive wear and may also cause the moving mechanism to jam. Since gear drives are commonly used in instances of high load requiring the transmission of high torque or high power, expensive and precise gear parts are required.
Therefore, a need exists for a new mechanical drive arrangement for radially arranged glass filter panels which exhibits zero backlash, low friction and low cost. The drive arrangement must provide a known and repeatable kinematic relationship between its moving parts so as to be reliable and durable.